#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
using namespace std;

const int N = 1e6 + 10, INF = 0x3f3f3f3f;

int n;
string s;

void solve()
{
    while (cin >> n) {
        cin >> s;
        int ans = 0;
        for (int i = 0;i < s.size();i++) {
            if (s[i] == '2' && s[i + 1] == '0' && s[i + 2] == '2' && s[i + 3] == '0')
                ans++, i = i + 3;
        }
        cout << ans << '\n';
    }
}

signed main()
{
    //ios::sync_with_stdio(0);
    //cin.tie(0);cout.tie(0);
#define ONLINE_JUDGE
#ifndef ONLINE_JUDGE
    std::istringstream in(R"()");
    std::cin.rdbuf(in.rdbuf());
#endif
    int T = 1;
    //cin>>T;
    for (int i = 1;i <= T;i++) {
        solve();
    }
}